University Archives

Dental materials are continuously improving with advancements in digital dentistry and 3D-printing technologies. Since dental materials undergo multiple stresses, exploring their mechanical properties is essential before clinical use. Our previous study determined there was no statistically significant difference found between 3D-printed denture base material thicknesses of 2.5 and 3.5 mm, so this study compares the transverse strength of different 3D-printing orientations with samples 2.5 mm thick. 

Objective: This study aimed to compare the transverse strength of a 3D-printed 2.5 mm-thick denture base material across three printing orientations. 

Methods: Thirty 3D-printed specimens (Formlabs denture base resin, Formlabs Inc., MA, USA), 50 mm x 25 mm x 2.5 mm, were fabricated using a low-force stereolithography (LFS) technology (Formlabs Form 3/Form 3B) at 0°, 45°, and 90° printing orientations, with autogenerated supports following manufacturer recommendations for washing and curing cycles. All specimens were finished, polished, and standardized with an electronic caliper (Kynup, LF04, Zheijang, China). The specimens were subjected to a three-point flexural test using an Instron universal testing machine (Instron 5565, Instron Corp), loading at a crosshead speed of 5 mm/min until failure. A one-way ANOVA was performed, followed by Welch’s ANOVA as a robustness check due to borderline variance heterogeneity. Statistical significance was set at α = 0.05. 

Results: Specimens printed at 90° showed the highest mean flexural strength (123.57 ± 13.39 MPa), followed by those printed at 0° (88.61 ± 27.06 MPa). The 45° orientation had the lowest mean flexural strength (76.82 ± 22.20 MPa) and the greatest variability. Orientation accounted for a small to moderate proportion of variance based on effect size analysis (η² = 0.069). However, no statistically significant differences were detected among groups by one-way ANOVA (p = 0.381) or Welch’s ANOVA (p = 0.497). 
Conclusion: There is no statistically significant difference observed between the transverse strengths of the 0°, 45°, and 90°. Clinically, these findings suggest that a 2.5 mm-thick 3D-printed denture base demonstrates adequate mechanical strength across all orientations and that clinicians and dental technicians can select a printing orientation based on practical considerations without increasing the risk of flexural failure.